Endodontics or root canal therapy (RCT) IS a part of dentistry sciences that is generally indicated for teeth having sound external structures but diseased, dead or dying dental pulp and/or related tissues. Such teeth mayor may not generally possess intact enamel and dentin and are satisfactorily engaged with surrounding bone tissue. A common aspect of endodontics comprises the treatment of such microorganism infected root canal systems. This procedure involves the dental clinicians' access to the root canal, removal all of the tooth pulp space contents comprising potentially infected and diseased tissues, microorganisms and their by-products from the root canal system of a tooth, disinfecting the root canal using chemo-mechanical techniques, and applying special root canal instruments and irrigation devices to enlarge the root canal space and remove irregularities or rough surfaces within the canal. After that, it is important to fill and seal the evacuated root canal in order to preserve the dead tooth from further reentrance of microorganisms and recurrent decay that might compromise the integrity of the tooth and cause recontamination and infectious disease. Thus the pulp tissue and excised portions of the root should be replaced by endodontic root canal filling materials which are materially safe, stable and biocompatible to living tissues thereby keeping the tooth root safe to periradicular tissues.
The most common root canal filling material is made from “Gutta-Percha” which is a natural resin and a thermoplastic rubber. A basic method involves inserting a preformed filling “cone” or “point” of gutta-percha into a root canal and the cone is laterally or vertically condensed into the canal, so that the point of the cone terminates at the apex of the canal. Remaining many irregularities on the surface and in the shape of canal even after root canal shaping, and the non-adhesive character of gutta-percha had made it impossible to achieve a satisfactory, completely and tridimensionally seal of the root canal system from any leakage of fluids, which may contain microorganisms, in the case of using this material alone.
The filling of the root canal can be further enhanced sealing by inserting sealants, flow able and lubricant materials, along with the gutta-percha points. An ideal root canal sealants should be biocompatible, anti-inflammatory, antibacterial, non-irritating, nontoxic, radiopaque, and have no or minimal shrinkage or even have a slight expansion. They must be preferably unaffected by moisture and to the chemical and physical conditions of the mouth. Ideal prepared sealant, have high wetting and low viscosity, facilitate insertion of filling material into the root canal so that seal the space between filling material and root canal walls. They should also set within a reasonable period of time.
Numerous sealants have been described, such as epoxy, calcium hydroxide and zinc oxide eugenol (ZOE) based sealers. During the root canal filling process, such materials are first applied to the gutta-percha and then inserted into the root canal along with each gutta-percha point or cone. Alternatively, they may be inserted using a file, reamer or lentalo applicator. In this manner, it is hoped that the remaining spaces between the gutta-percha points and the root canal walls can be filled and sealed with the appropriate sealant material. Controlling the exact amount of the sealant or filling material within the border of the root canal to avoid overextension or overfilling has been a challenge for dentists. In the case of overflow of root canal sealant from the apical foramen into the periradicular tissue during a root canal filling process, the excess material should be desirably tolerated by the surrounding tissue while it's better for it to stimulate tissue healing.
One of the drawbacks of using conventional sealants is that such materials tend to be hydrophobic. This makes such materials incompatible with somewhat moist dental hard (which are highly mineralized) and soft tissues within the root canal, which therefore extremely hydrophilic. Thus the hydrophilic nature of the root canal environment inhibits adequate penetrance, complete wetting, and efficient adhesion of the hydrophobic sealant to root canal walls. As a result, a poor seal will be actually observed between the gutta-percha cones and the root canal walls, therefore it may lead to reentrance of mouth microorganisms into the canal and help them to multiply, which subsequently can be finalized as reinfection or other unwished complications. Another point is that the overfilled gutta-percha and conventional sealant materials tend not to have tolerance but also irritate the periapical soft tissues and they do not stimulate healing and hard tissue formation. In addition to all above, these materials are degraded during long-term exposure of tissue fluids that are always present in the mouth.
While there are many techniques for root canal filling, as mentioned, the most widely used technique is the combination of gutta-percha cones and a sealant material. This technique has also been used with root-end fillings (also referred to as retrograde root canal fillings) during periradicular surgery and for the repair of tooth root perforations.
The function of an ideal root-end filling materials is preparing perfect sealing ability in order to interfere with the path of reinfection of microorganism or their byproducts completely, interrupting all paths between root canal system and its external surface. In addition, the root-end filling material should be antibacterial, nontoxic, noncorrosive, nonresorbable, dimensionally stable, easy handling, moisture indifferent, radiopaque, cost-effective, adaptable to the dentinal walls, and finally biocompatible and able to induce regeneration of the bone and periodontal attachment, specifically cementogenesis over the root-end filling itself.
The root-end filling material was used to be the gutta-percha, amalgam, reinforced zinc oxide eugenol cement such as intermediate restorative material (IRM) and super EBA, glass ionomer cement, and mineral trioxide aggregate (MTA). The gutta-percha operation was so difficult, although amalgam has been used for more than a century and has proven itself well tolerated by oral tissues; unfortunately its use is disadvantageous for several reasons: it stains soft and hard tissues, eventually leaks from corrosion, is dimensionally unstable, and moisture sensitive. Reinforced zinc oxide eugenol cements have demerit of releasing eugenol and high-solubility, the IRM weak point is its sensitivity to water, and the super EBA contained mass eugenol and the release of eugenol, high-solubility and inflammatory effect. The glass ionomer cement has sensitivity to water and moisture, the material property is being thick, hard to dense-filling, and its difficult handling. Although MTA has superior biocompatibility in comparison with the conventional root-end filling materials, it has delayed setting time, poor handling characteristics, off-white color, and also a high price.
In case of root perforation(s), the filling material should be able to fill the perforation site effectively and seal the avenue of communication between the oral cavity and the underlying periodontium apparatus. For example, in a multi root tooth, the fork at the junction of the roots forms a “bi or tri-furcation.” Thus, perforations in the furcation provide ready access of oral microorganisms to the tissues of the gum. In the case of root perforation the clinician can also apply root-end filling materials as mentioned before, so there is a need for a suitable perforation repair material in the art.
In contrast to endodontic procedures, in other certain dental procedures the pulp of the tooth is left intact. Where the pulp is exposed or partially damaged, a “pulp capping” or “pulpotomy” material is required which will preserve the vitality of the pulp. These materials must also be biocompatible, bioactive, nontoxic, and without any irritation to the pulp. An ideal pulp capping or pulpotomy compounds also allow the regeneration of surrounding tissue and dentine. Calcium hydroxide-based pulp capping or pulpotomy agents are therefore common. The calcium hydroxide technique has a very limited working time before setting. This material is degraded by long-term exposure to tissue fluids that are commonly present in the mouth and also is not impervious to moisture. It is difficult to form a hermetic seal with the calcium hydroxide filling materials. Therefore a need for pulp capping and pulpotomy materials remams which are biocompatible, bioactive, nontoxic, and are capable to stimulate dentin-like tissue formation.
A critical factor in the long-term success of endodontic therapy involves eliminating the leakage around and through a pulp capping or pulpotomy agent, root canal sealant, root canal filling, root-end filling, or the perforation repair material. Intimate adaptation of the filling material to the cavity walls typically plays an important role in elimination of the leakage. However, attaining intimate adaptation is difficult. Therefore, it is desirable to provide compositions and methods which improve the ability of penetrance, wetting, adaptation, filling, and sealing the dental soft and hard tissues surrounding the tooth cavity or root canal system for an endodontic filling material particularly in presence of moisture or water. Having antimicrobial effects and the ability to reduce or eliminate microorganisms, by-products, and their leakage would be an advantage for endodontic filling materials. Biocompatibility, of course, deserves to be mentioned as a high valuable point for these materials. It would be also highly beneficial if the endodontic filling material could be bioactive and stimulus for the repair and regrowth of the potentially surrounding soft and hard tissues so that the dental-like hard tissues will be formed.
Such compositions and methods for more effective filling and sealing of a tooth cavity or root canal system are disclosed and claimed herein.